The evolutionary significance of polyploidy

Polyploidy occurs frequently but is usually detrimental to survival; thus, few polyploids survive in the long term. Here, evidence linking the short-term evolutionary success of polyploids to environmental upheaval is reviewed and possible longer-term evolutionary benefits of polyploidy are discussed. Polyploidy, or the duplication of entire genomes, has been observed in prokaryotic and eukaryotic organisms, and in somatic and germ cells. The consequences of polyploidization are complex and variable, and they differ greatly between systems (clonal or non-clonal) and species, but the process has often been considered to be an evolutionary 'dead end'. Here, we review the accumulating evidence that correlates polyploidization with environmental change or stress, and that has led to an increased recognition of its short-term adaptive potential. In addition, we discuss how, once polyploidy has been established, the unique retention profile of duplicated genes following whole-genome duplication might explain key longer-term evolutionary transitions and a general increase in biological complexity.